I've had this so much, and it drives me round the bend - he's not hungry, he can't be hungry, don't feed him, distract him....
I think it's three things - one, treating small babies as if they are older children, or adults, even, and capable of quite complicated and manipulative behaviour. When they just aren't.
Two - the prevalence of scheduled formula feeding. It's just so dominant. My MiL, while broadly supportive of BF-ing, still says 'what time does he feed', 'when is his next feed', 'if he feeds now, he won't be hungry when it's time for his next feed...' She just doesn't fundamentally understand BF-ing on demand.
Three - I've come to think that SO many women's attitude towards food and feeding is in general is so complicated, they end up projecting them onto babies. Seriously. Telling a baby off for being greedy, or 'snacking', or telling them they've had enough and they must 'learn to go without' for a bit.... it's all the language of moral 'dieting' judgement, and I honestly think a whole host of borderline eating disorders came round with their owners to hover over my baby's head when he was tiny.
None of which should be my baby's problem.